Supplemental signaling system for special railway vehicle



Feb. 4, 1958 H. A. THOMPSON SUPPLEMENTAL SIGNALING SYSTEM FOR SPECIAL RAILWAY VEHICLE Original Filed Sept. 25, 1948 2 Sheets-Sheet l n .w N o H m 0 Z W MT 6 M n mm i 6% R%\ Feb. 4, 1958 H. A. THOMPSON SUPPLEMENTAL SIGNALING SYSTEM FOR SPECIAL RAILWAY VEHICLE 2 Sheets-Sheet 2 Original Filed Sept. 25, 1948 N5 A r w l KN F m m psgw m ,m N k FH E IF d r w w "W Q N w H H fiwwxmw H PNU Q -MN NN um wm 5% m m \uxmmw AUD A. EN 5% United States Patent ce SUPPLEMENTAL SIGNALING SYSTEM FOR SPECIAL RAILWAY VEHICLE Howard A. Thompson, Edgewood, Pa., assignor to Westinghouse Air Brake Company, Wilmer-ding, Pa., a corporation of Pennsylvania Original application September 25, 1948, Serial No. 51,276, now Patent No. 2,617,922, dated November 11, 1952. Divided and this application May 20, 1952, Serial No. 288,802

6 Claims. (Cl. 246-33) My invention relates to railway signaling systems, and particularly to supplemental signaling systems for governing the movement of special railway vehicles which move independently of the usual block signal systems.

Special railway vehicles, such as small motor cars used by maintenance men, are usually equipped with insulated wheels or axles so that these cars will not shunt the track circuits of signaling systems which govern train movements. As a result, the conventional railway signaling systems do not protect the operator of a motor car or other special vehicle of that character.

This application is a division of my copending application for Letters Patent of the United States, Serial No. 51,276, filed September 25, 1948, now Patent No. 2,617,922, granted November 11, 1952, for Supplemental Signaling Systems for Special Railway Vehicles. The

system of the present application is an improvement upon those described in the copending application for Letters Patent of the United States, Serial No. 996, filed January 7, 1948, by Wilbur V. Grosjean, now Patent No. 2,630,524, granted March 3, 1953, and in Letters Patent of the United States No. 2,528,052, granted October 31, 1950, to Wilbur V. Grosjean, both of which are entitled Supplemental Signaling System for Special Railway Vehicles.

An object of the present invention is to provide an improved supplementary signaling system for indicating to operators of special vehicles of the type described that a train is approaching.

Another object is to provide an improved supplementary signaling system for the continuous control of moving vehicles of a special character which may be superimposed without interference upon a conventional cab signaling or train control system for the continuous inductive control of standard railway vehicles. a

A further object is to provide an improved supplemental signaling system for the operation of special wayside indicators which govern the movement of special vehicles only.

A further object of my invention is to provide an improved supplemental signaling system including means for preventing a receding train from giving a false indication that a train is approaching.

My invention is disclosed herein as applied to a conventional block signal system adapted for use on each track of a multiple-track railway, which block signal system controls movements over the track in one direction only. The system disclosed employs conventional direct current track circuits and supplies coded alternating current to the track rails for the control of train-carried cab signaling or train control equipment of the continuous inductive type, such as is shown, for example, in Letters Patent of the United States No. 1,986,679, issued January 1, 1935, to Lloyd V. Lewis for Railway Traffic Controlling Apparatus.

In the supplemental signaling system described herein,

the special vehicles are each provided with .a receiving relay responsive to alternating current in the track rails 2,822,463 .Patented Feb. 4, 1958 which controls visual and audible indicators. The motor car carried apparatus is so arranged that a lamp is steadily lighted as long as the relay is energized by steady alternating current supplied to the track rails, thus indicating to the operator that no train is approaching from either direction. The lamp is extinguished and an audible signal is sounded when the supply of current is interrupted.

It follows that either the absence of alternating current or the presence of alternating current interrupted at a specified rate, such as times per minute, as provided for the control of the cab signals on an approaching train constitutes a warning to the operator of a motor car that the motor car should be removed from the track.

In the signaling system described herein, wayside motor' car indicators are provided for the control of the special railway vehicles, in addition to the indicators carried by the motor cars themselves. This supplemental signaling system utilizes line circuits extending between successive signal locations and forming part of the conventional block signaling system. In the supplemental system, a

series approach relay is added at the advance or energy tacts in the corresponding second line circuit extending one. block further in advance, while the biased polar re lay operates means for controlling an adjacent wayside indicator and for controlling the supply of motor car indicator current to the track rails of the section through which its circuit extends. The operation is such that when a train enters a given section, it deenergizes the signal and also the series approach relay in the signal circuit at the location of the next signal in advance which opens the second line circuit extending to the location of the second signal in advance, deenergizing both the polar and neutral relays at that location. Deenergization of that neutral relay pole-changes the second line circuit extending to the location of the third signal in advance, thereby deenergizing the polar relay at that location. Since each polar relay controls the motor car warning indication for its particular section, it will be seen that a train moving in the normal direction will indicate its approach to a motor car occupying either of the two block sections ahead of the one occupied by the approaching train.

Although the signal system is arranged for the control of train movements in one direction only, it is assumed that at times train movements in the opposite direction will be made. The motor car indicator system provides protection for such train movements by utilizing the signal control circuits to cut off the motor car indicator current from the rails of a section in the rear of a signal which indicates caution or stop, that is to say, from the rails of the two sections ahead of attain which is moving in the direction opposite to the normal direction. Directional stick relays at each signal location prevent cutting off the motor car indicator current in this manner from' equipped with a conventional block signaling system and: also with a supplemental signaling system incorporating my invention. Fig. 2 is a diagrammatic view of oneform,

ofindication equipment which may be carried on a rail:

way motor car or other special vehicle to be used in cooperation with the wayside apparatus of my invention.

Similar reference characters refer to similar parts in each of the several views.

Figs. 1A and 1B In Figs. 1A and 13 a stretch of railway track is shown to which my supplemental signaling system for special vehicles is applied. This stretch of track represents one track of a double-track railway, which is equipped with conventional wayside signals for single direction running only and also with cab signals for single direction running. The supplemental signaling system shown therein warns operators of motor cars when a train is approaching from either direction, but does not inform the motor car oper ator as to the direction of approach.

The Figures 1A and 13 may be placed end to end either with Fig. 1B at the right of Fig. 1A or with Fig. 13 at the left of Fig. 1A.

The stretch of track shown is divided into sections 12T, 14T, 16T and 18T, located immediately in advance of signals 12, 14, 16 and 18, respectively. Each section is provided with the usual normally closed track circuit including a track relay TR at one end energized by a track battery TB connected across the rails at the other end.

Circuit elements associated with a particular track section are indicated by alphabetical reference characters designating the type of element prefixed by numerical reference characters corresponding to the number of the particular section. For example, 6TR indicates the track relay TR for section 6T.

Each track section is provided with a track transformer TT, which has its secondary winding connected across the track rails in series with the track battery. Each transformer TT supplies cab signaling current to the rails for the control of eastbound trains when alternating current is supplied to its primary winding. The windings of the track relays present a high impedance to the alternating current, so that the alternating current flowing through the track relay windings is negligible. Hence, alternating electrical current may be supplied to a track section without affecting the operation of the direct current track circuit in that section.

A local battery or other suitable source of direct current is provided at each signal location to energize the circuits other than the track circuits. These sources are not shown in the drawings, but their positive and negative terminals are designated B and C, respectively. A source of alternating current, not shown, is also provided at each signal location, the terminals of which are designated BX and CX.

At each signal location a code transmitting relay is provided for cab signal purposes, which is identified by the reference character 180CT in the drawings. This reference character indicates that the code transmitting relay opens and closes its contacts 180 times per minute.

The motor car indication system of Figs. 1A and U3 not only governs the indicators carried on the cars, but also governs wayside indicators 12MC, MMC, 163/16 and 18MC. These wayside indicators may be, for example, of the type shown and claimed in Letters Patent of the United States No. 2,500,608, granted to Arthur W. Fisher and Wesley B. Wells on March 14, 1950, for Wayside Indicator for Railway Motor Cars.

Thenormal direction of traffic movement on the stretch of railway track shown in Figs. 1A and 1B is eastbound, or from left to right in the drawings, as indicated by the arrows. The signals 12, 14, 16 and 18 control eastbound traffic only, no wayside signals being provided for westbound trafiic.

The signals 12, 14, 16 and 18 are conventional color light signals having green, yellow and red lamps G, Y and R having lighting circuits which are governed in the manner shown for signal 12. When the track relay,

4 such as relay 12TR for the section directly in advance of the signal, is released, its lamp R is lighted to indicate stop. When this track relay is energized, lamp Y is lighted to indicate caution provided an associated line relay 12DR is released, and lamp G is lighted in place of lamp Y to indicate proceed when the line relay is encrgized. Each line relay DR is controlled over a line circuit governed by the track relays for two sections in advance, as illustrated by the circuit for relay 12DR, which may be traced from the positive terminal B of the battery at the location of signal 14 through the winding of a series approach relay 14XR, over front contact b of the track relay 14TR, line wire 17, front contact 0 of the track relay 12TR, the winding of relay 12DR, and thence over a common return line wire CL to the negative terminal C of the battery at the location of signal 14.

The XR relays have been included in the signal line circuits for the purposes of my improved motor car indication control system, and control a second series of line circuits.

Each line circuit of this second series includes at its left-hand end, a source of current, pole-changing contacts of a line relay YR and a front contact of the adjacent approach relay XR, and at its right-hand end includes the windings of an indication control relay ZR and of the corresponding line relay YR at that end. Each relay ZR is of the biased polar type responsive to energy of one polarity only and picks up only when the controlling relays XR and YR are both energized. The relays YR are ordinary neutral relays and are repeaters of the controlling relays XR, and each is connected to its line circuit through a rectifier 20 to prevent its momentary release during a reversal of the polarity of the line current by the line relay YR which governs that circuit.

The line circuit of the second series extending between the locations of signals 12 and 14 may be traced from the positive terminal B of a battery at the location of signal 12 over a front contact a of relay 12YR, line wire 19, front contact b of relay 14DR, front contact at of relay 14TR, through the winding of relay 14ZR, rectifier 20 and the winding of relay 14YR, line wire 21, a front contact of relay 12XR, and front contact b of relay 12YR to negative terminal C of the battery at the location of signal 12. When relay IZYR is deenergized, the polarity of the energy supplied to the line circuit just traced is reversed, in which case relay 14YR remains picked up, since due to the rectifier 20 the direction of current through its winding remains unchanged, while relay 14ZR assumes its released position due to the fact that it is responsive to current of normal polarity only.

A branch circuit is provided for at times shunting the front contact b of relay 14DR and the front contact d of relay 14TR in the line circuit under discussion. This branch circuit may be traced from line wire 19 over a front contact a of a directional stick relay 148 to the right-hand terminal of the winding of relay 14ZR. The contact b of relay 14DR and contact at of relay 14TR are provided in order to deenergize relay 14R whenever a train approaches from a direction opposite to the normal direction of traffic. The stick relay 14S and its contact a are provided to prevent such deenergization of relay 14ZR by an eastbound train moving in the normal direction and receding from the location of signal 14.

The circuits for the directional stick relays S are conventional. The pickup circuit for relay may be traced from the positive battery terminal B at location 14 over back contact e of track relay 14TR, front contact c of relay I i-DR, and thence through winding of relay MS to negative battery terminal C. The stick circuit of relay MS may be traced from the same positive battery terminal B through either back contact e of relay 14TR or back contact 0 of relay 14DR, and thence through front contact b of stick relay 14S, and the winding of relay 148 to negative battery terminal C. The pickup circuit for relay 148 is closed whenever a train moving from left to right passes signal 14. The stick circuit for relay 145 is then completed through its front contact b and remains completed until relay 14DR agaln picks up upon the departure of the train from sections MT and MT. The stick relay 14S therefore holds its contact a closed as long as contact 0 of relay 14DR is maintained open by deenergization of relay 14DR.

The wayside motor car indicator 14MC is energized over the line wires 19 and 21 through an obvious circuit which includes a front contact a of relay 14ZR.

The relay 142R also controls a contact b which selectively supplies the primary winding of a track transformer 12TT with steady alternating electrical current for motor car indication purposes when the relay 14ZR is energized or with coded alternating electrical current for cab signal purposes when the relay 14ZR is deenergized.

The circuit for supplying steady alternating current for motor car indication purposes to transformer 12TT may be traced from one terminal BX of the local alternating current supply through front contact b of relay 14ZR, and primary winding of transformer 12TT to the opposite terminal CX of the alternating current supply.

The circuit for supplying coded cab signal current to transformer winding 12TT may be traced from another terminal BX of the alternating current supply over a contact of a code transmitter 180CT, a front contact 1 of track relay 141" R, back contact b of relay 142R, and the primary winding of transformer 121T to terminal CX of the alternating current supply.

The secondary winding of transformer 12TT is connected in series with the track battery 12TB and the usual current limiting impedance across the rails of section 121 at its exit end.

Fig. 2

Referring now to Fig. 2, a diagrammatic view of one arrangement of indication apparatus is there shown which may be employed on motor cars or other special vehicles which are operated over the stretch of track .described above. As indicated diagrammatically in Fig. 2, the wheels W1 and W2 are insulated from theframe of the vehicle and from each other by interposing insulated bushings and washers 2 between the wheels and the axle AX. It is to be understood that the other pair of wheels, not shown, on the motor car are similarly insulated, so that the car will not shunt a track circuit. A slip ring SR1 is electrically connected'with the wheel W1 and a second slip ring SR2 is electrically connected with the wheel W2. Connected in series between the slip rings SR1 and SR2 are the condenser IQ and the primary winding of a transformer ITT. The secondary winding of the transformer ITT is connected to the input terminals of a bridge-type rectifier IRX, and the winding of an indicator relay IR is connected across the output terminals of this rectifier. It will be apparent that when the car moves over the rails of a track section the condenser 1Q will block the flow of direct. cur rent track circuit energy, but will permit the flow of alternating current from one track rail to the other through the primary winding of the transformer ITT. The alternating current induced in the secondary winding of transformer ITT is rectified by rectifier IRX, and is supplied to the winding of relay IR, and as a result, relayIR picks up to establish a circuit, obvious from thedrawing, for supplying energy over its front contact from the battery 13 to light the indicator lamp KE. If the supply of alternating current to the rails R is interrupted, current is no longer supplied to the winding of relay IR and its contacts release, extinguishingthe lamp KB, and establishing a circuit for supplying energy to a warning bell KS. A switch SW is shown in series with the circuit for supplying energy to the indication lamp KB and the warning bell KS, so that the equipment may be deenergized when the car is removed from the rails.

It is to be understood that my invention is not limited to the specific arrangement of vehicle carried indicator equipment shown in Fig. 2, and any suitable'indicator means may be employed which will detect a distinctive indicating current supplied to the track rails and distinguish that current from the current used to energize the track relays. When'alternating current is employed, as shown herein, the relay IR may be made responsive to current flowing in the track rails by the provision of receiving coils on the motor car in inductive relation to the rails, together with an amplifier for amplifying the energy induced in such coils, such an arrangement being well known from its use for the control of train-carried cab signals, as shown in the Lewis Patent No. 1,986,679 hereinbefore referred to.

It will be seen that if a car equipped with apparatus as shown in Fig. 2 travels over the stretch of trackshown in Figs. 1A and 1B at a time when the system is in its normal condition with all of the track relays picked up, each of the track sections will in turn supply steady alternating current to the apparatus on the car and the relay IR on the car will remain energized, thus causing the lamp KE to remain lighted, and thereby indicate to the operator of the motor car that he may safely continue running.

It will be readily apparent, however, that the system of my invention differs very materially from the conventional cab signaling systems for the continuous control of train movements by apparatus responsive to alternating current in the track rails. In such systems, the track relay for the occupied section is shunted by the wheels and axles of the train, which complete a path from rail to rail for the cab signaling current supplied to the rails at the end of the section which is in front of the train.

The motor car indication current on the other hand is supplied in such a manner that for either direction of motor car operation, its circuit is eifectively completed from rail to rail as indicated in Fig. 2 only in the absence of a train shunt. That is to say, the motor car current is supplied to the rails of a section over a circuit governed by the front contacts of the track relay for the section at a time when cab signaling current is not needed. It follows that a cab signaling system which embodies the approach control principle in which the control current is supplied to the rails of a section in response to the release of the track relay may be used in conjunction with my motor car indicator system without interference, merely by a choice of currents of different characteristics for the two systems.

Operation Let it be assumed that a train proceeding in the normal eastbound direction of trafiic is proceeding through the track stretch with the signals ahead indicating proceed, and is just entering the track section 12T. The conventional wayside signal system operates in the usual manner, and a detailed discussion of it is believed to be unnecessary here. Briefly, occupancy of any track section by a train deenergizes its track relay and sets the signal at its entrance end to stop. Deenergization of the track relay also opens the line circuit to the DR relay for the next signal in the rear, so that that signal is set to its caution position. The second and following signals in the rear of the occupied section will then indicate proceed.

When the train enters section 12T, relay 12TR releases to cause the display of a stop indication by signal 12, and opens its front contact 0 in the line circuit for relay 12DR which includes wires 17 and CL and the winding of relay 14XR at the next signal location in advance. Relay 14XR releases, opening its contact in the line circuit extending over line wires 22 and 23 to the location of signal 16, which is the second signal in advance of the occupied track section. Relays 16ZR and 16YR therefore release, but since relays 14TR and 16TR are picked up, relay 16XR is energized in series with relay 14DR over line Wires 24 and CL and completes the line circuit which includes wires 25 and 26. Since relay 16YR is released, its pole-changing contacts a and b supply current of reverse polarity to this line circuit which extends to location of signal 18, the third signal in advance of the occupied track section. Current of reverse polarity flowing in this circuit causes the biased polar relay lSZR to release, but maintains relay 18YR energized. Relay 18XR is energized in series with relay lDR over line wires 27 and CL, allowing relay 18YR to supply current of normal polarity over line wires 28 and 29 to the location of the fourth signal in advance of the occupied section to energize relays corresponding to relays 12YR and 122R at that location, the relay corresponding to relay 12XR at the fourth location being energized in series with relay 18DR over line wire 30.

he release of relay 18ZR opens the energizing circuit for motor for motor car indicator 18MC at its contact a, and its contact b inserts a contact of a code transmitter ISOCT in the circuit for the primary winding of transformer 161T, so that coded alternating current for cab signal control is supplied to the rails of section 16T in place of steady alternating current for motor car indication control.

Since at this time relay 162R is deenergized, as above described, its motor car wayside indicator 16MC is set to stop and its contact b operates to discontinue the supply of steady alternating current to transformer MTT and substitutes the coded cab signal current.

The energizing circuit for relay 14ZR is opened at the front contact of relay 12XR, which relay was released by the track relay for the section in the rear of section 12T and is now held deenergized by the opening of front contact b of relay 12TR. Consequently, wayside motor car indicator 14MC is also set to stop, and the motor car indication current is removed from transformer 12TT and replaced by the coded cab signal current.

When the train above referred to entered section 12T, stick relay 12S picked up and its contact a bridges contact b of relay lZDR and contact d of relay 12TR in the energizing circuit for relays 12YR and 122R which includes line wires 28 and 29 and is held open by relay 18XR for section 1ST in the rear of section 1.2T, relay 18XR being held released by the track relay 18TR until the train vacates that section. If there is no second train following the one in section 12T to maintain relay 18XR released, relays IZYR and 12ZR then become energized. Under this condition relay i2ZR will cause indicator 12MC to display a clear indication as soon as the train vacates the section in the rear, and will cause steady alternating current to be supplied through transformer ISTT over front contact I) of relay 122R to the rails of the section in the rear of the one occupied by the receding train.

When the train enters section 14T, relay 14TR releases and causes the indication of signal 14 to change from proceed to stop. The opening of contact 1 of relay 14TR cuts off the supply of coded current to the rails of section 121", and relay 14S picks up over back contact 2 of relay MTR. In addition, the opening of contact of relay MTR releases relays 14DR and 16XR, and relay 16XR deenergizes relays ISYR and 18ZR, the latter relay being already in its released position. Relay 18YR reverses the polarity of the current supplied over line wires 28 and 29 to the relays IZYR and 12ZR at the next location in advance, and this relay 122R releases to display a warning indication by the release of its indicator IZMC and to supply coded cab signal current in place of steady current to the railsof its section.

When the train vacates the rear section 112T, its track relay 12TR picks up to cause the indication of its signal 12 to change from stop to caution. Relays 12DR and I4XR are held released by the opening of contact b of relay 14TR, and relay 125 is held energized over back contact c of relay 12DR. If'there is no following train within its control limits, relay 12XR picks up over contact 8 b of relay 12TR, and if relay 12YR is also energized, relays 14YR and 142R pick up over contact a of relay 14S. Relay 142R then energizes indicator MMC and supplies steady alternating current to the rails of section 12T.

When the train advances into section 16T, the indication of signal 16 changes from proceed to stop, the supply of coded current to section MT is cut off, relay 16S picks up, and relays 16DR and 18XR release, due to the release of relay 16T R. In front of the train, relay ISXR deenergizes relays 12YR and 12ZR at the next location in advance and relay 12YR releases relay 14ZR to extend the motor car warning limit to include the second location in advance.

When the train in section 161 vacates the rear section 14T, its track relay 14TR picks up to cause the indication of signal 14 to change from stop to caution, and to reenergize relays 12DR and 14XR. Relay 12DR causes the indication of the rear signal 12 to change from caution to proceed, and releases relay 128. If there is no train following the one in section 16T, relays 12YR and 12ZR in the rear are maintained energized over contact at of relay 12DR and contact b of relay 12TR, and relays 14YR and 14ZR are energized over contact a of relay 14S. Relays 16Y R and 16ZR pick up, due to the energization of relay 14XR, and relay 16ZR energizes indicator 16MC and supplies steady alternating current to the rails of section 14T.

From the foregoing, it may be seen that an eastbound train occupying a track section deenergizes the wayside motor car indicators at the three signal locations in advance of the occupied section, and causes the supply of steady alternating electrical current, the presence of which indicates to a motor car operator that no train is approaching, to be cut off from the rails of the section occupied by the train and from the rails of the two sections in advance, and also causes coded alternating current for cab signal purposes to be supplied to the rails of these sections.

Consider now the conditions which occur when a train is moving westwardly, opposite to the normal direction of traflic through the stretch of track shown in the drawings. Let it be assumed that a westbound train is entering section 161. The shunting effect of its wheels and axles prevents transformer 16'IT from supplying current to the rails of that portion of section 16T which is in front of the train, and also deenergizes track relay 16TR, which opens its contact d in the circuit of relay 16ZR. De-

. energization of relay 162R sets the wayside motor car indicator 16MC to stop, and interrupts the supply of steady alternating current to transformer 14TT. The supply of coded cab signal current to transfer 14TT is interrupted at front contact of relay 16TR.

At the same time, opening of contact b of relay 16TR opens the circuit of relay 14DR. Relay 14DR releases and its contact b opens the energizing circuit of relay 14ZR. Wayside motor car indicator 14MC is therefore also set to stop and the supply of current to track transformer 12TT is changed from steady to coded alternating current.

It may therefore be seen that a westbound train deenergizes the wayside motor car indicators at two locations. in advance and removes the motor car indication current from two track sections in advance.

It will also be seen that for either direction of train movement, when a train enters a block section the zone of motor car protection is extended to include three full sections in advance of the train, this zone decreasing to two sections as the train approaches the exit end of the section through which it is moving.

Although I have shown in this system the use of both wayside motor car indicators, such as those indicated at MC in the drawings, and car-carried indicators such as illustrated in Fig. 2, it should be understood that either oneof these maybe used to the exclusion of the other, if desired.

The cab signal system illustrated herein gives to the engineman an indication of the condition of the next track section in advance, as to whether or not it is occupied. For example, the supply of cab signal energy to transformer 12TT is controlled by front contact 1 of relay 14TR. Accordingly, the cab signal energy is supplied to the rails of section 12T only if section 14T is unoccupied. The back contacts b of the ZR relays in this system provide approach control for the cab signals, and it will be seen that the cab signal current is supplied to the rails of a given section only when a train is within or approaching that section.

Although I have herein shown and described only one signaling system embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized by current supplied to the rails of its section and which releases due to the shunting effect of the wheels and axles when a train occupies its section, a signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relays, comprising means for indicating to the operators of said special vehicles that no train is approaching the section in which they are located, a first series of line circuits, each circuit of said first series extending between the entrance ends of adjacent track sections and including front contacts of the track relays of said adjacent track sections and the winding of an approach relay at the advance end of the line circuit; a second series of line circuits, each circuit of said second series extending between the entrance ends of adjacent track sections and including at its advance end the winding of a biased polar relay and the winding of a neutral relay, and at the entrance end a front contact of the approach relay at that location and pole-changing contacts operated by the neutral relay at that location; so arranged that each biased polar relay is energized only when the approach relayand the neutral relay which control its circuit are both energized and each neutral relay is energized whenever the approach relay which controls its circuit is energized; and means actuated by each such polar relay when energized for energizing the indicating means of its associated section.

2. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized by current supplied to the'rails of its section and which releases due to the shunting etfect of the wheels and axles when a train occupies its section, a signaling system for the protection of'spe'cial'vehicles in said stretch which are not adapted to shunt said track relays, comprising means for indicating to the operators of said special vehicles that no train is approaching the section in which they are located, a first series of line circuits, each circuit of said first series extending between the entrance ends of adjacent track sections and including front contacts of the track relays of those sections and the winding of an approach relay at the advance end of the line circuit; a second series of line circuits, each circuit of said second series extending between the entrance ends of adjacent track sections and including at itsadvance end the winding of a biased polar relay and the winding of a neutral relay, and at the entrance end a front contact of the approach relay at that location and pole-changing contacts operated by the neutral relay at that location, so arranged that when a train entering one section deenergizes the track relay thereof, said deenergization releases the approach relay at the entrance end of the first section in advance, the neutral relay at the entrance end of the second section in advance, and the biased polar relay at the entrance and of the third section in advance; and means actuated 10 by each such polar relay when energized for energizing the indicating means of its associated section.

3. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized by current supplied to the rails of its section and which releases due to the shunting effect of the wheels and axles when a train occupes its section, said stretch being provided with a signaling system including wayside signals controlled by said track relays for governing the movement of trains through said stretch, a supplementary signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relays, comprising a wayside indicator in each section for signaling to the operators of said special vehicles that no train is approaching, a first series of line circuits, each circuit of said series extending between the entrance ends of ad jacent track sections and including front contacts of the track relays of those sections and the winding of an approach relay at the advance end of the line circuit; a second series of line circuits, each circuit of said second series extending between the entrance ends of adjacent track sections and including at its advance end the winding of a polar relay and the winding of a neutral relay, and at the entrance end a front contact of the approach relay at that location and pole-changing contacts operated by the neutral relay at that location; so arranged that when a train entering one section deenergizes the track relay thereof, said deenergization causes the release of the approach relay at the entrance end of the first section in advance, said approach relay releases the neutral relay at the entrance end of the second section in advance and said neutral relay reverses the polarity of the current supplied to the polar relay at the entrance end of the third section in advance; and means operated by each polar relay for operating the wayside indicator of its associated section.

4. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized by current supplied to the rails of its section and which releases due to the shunting effect of the wheels and axles when a train occupies its section, said stretch being provided with a signaling system including wayside signals controlled by said track relays for governing the movement of trains in one direction through said stretch, a supplementary 'signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relays, comp-rising means for indicating to the operators of said special vehicles that no train is approaching the section in which they are located, a first series of line circuits, each line circuit of said series extending between the entrance ends of adjacent track sections and including front contacts of the track relays of those sections, the winding of a signal relay at the entrance end of the line circuit, and the winding of an approach relay at the advance end of the line circuit; a second series of line circuits, each line circuit of said second series extending between the entrance ends of adjacent track sections and including at its advance end the winding of a polar relay, the winding of a neutral relay, and front contacts of the track and signal relays at said advance end, and at the entrance end a front contact of the approach relay at that location and pole-changing contacts operated by the neutral relay at that location; so arranged that a train occupying one section deenergizes the track relay thereof, said track relay releases the approach and polar relays at the entrance end of the first section in advance, said approach relay releases the neutral and polar relays at the entrance end of the second section in advance and said neutral relay by reversing the polarity supplied thereto releases the polar relay at the entrance end of the third section in advance; said track and signal relays being effective upon movement of a train through said stretch in the opposite direction to deenergize the polar relays for 11 two sections in advance of the one occupied by the train moving in said opposite direction, and means operated by each polar relay for operating the indicating means of its associated Section.

5. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized by current supplied to the rails of its section and which releases due to the shunting elfect of the wheels and axles when a train occupies its section, said stretch being provided with a signaling system including wayside signals controlled by said track relays for governing the movement of trains in one direction through said stretch, a supplementary signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relays, comprising means for indicating to the operators of said special vehicles that a train is approaching the section in which they are located, a first series of line circuits, each line circuit of said series extending between the entrance ends of adjacent track sections and including front contacts of the track relays of those sections, the winding of a signal relay at the entrance end of the line circuit, and the winding of an approach relay at the advance end of the line circuit; a second series of line circuits, each line circuit of said second series extending between the entrance ends of adjacent track sections and including at its advance end the winding of a polar relay, the winding of a neutral relay, and a front contact of the signal relay at said advance end, and at its entrance end a front contact of the approach relay at that location and pole-changing contacts operated by the neutral relay at that location; arranged so that a train occupying one section deenergizes the track relay thereof, said track relay deenergizes the signal and polar relays at its location and at the location of the next signal at the rear and also deenergizes the approach and polar relays at the entrance end of the first section in advance, said approach relay releases the neutral and polar relays at the entrance end of the second section in advance, and said neutral relay releases the polar relay at the entrance end of the third section in advance; said signal relays being effective upon movement of a train through said stretch in the opposite direction to deenergize the polar relays two sections in advance of the one occupied by the train moving in said opposite direction, means operated by each polar relay for operating the indicating means of its associated section to indicate the approach of a train, and directionally controlled means for each section effective to prevent deenergization of the polar relay for the section in the rear when the adjacent signal relay is deenergized by a receding train.

6. In combination with a stretch of railway track divided into a plurality of sections each having a track relay which is normally energized by current supplied to the rails of its section and which releases due to the shunting effect of the wheels and axles when a train occupies its section, said stretch being provided with a signaling system including wayside signals controlled by said tra'ck relays for governing the movement of trains in one direction through said stretch, a supplementary signaling system for the protection of special vehicles in said stretch which are not adapted to shunt said track relays, comprising means for indicating to the operators of said special vehicles that a train is approaching the section in which their vehicles are located, a first series of line circuits, each circuit of said series extending between the entrance ends of adjacent track sections and including at its advance end the winding of an approach relay and at its entrance end the winding of a signal relay, each such circuit also including from contacts of the track'relays of said, adjacent sections; means operated by each signal relay for governing the operation of the wayside signal at that location, a second series of line circuits, each line circuit of said second series extending between the entrance ends of adjacent track sections and including at its advance end the winding of a polar relay, the winding of a neutral relay, and a front contact of the signal relay at said advance end, and at its entrance end a front contact of the approach relay at that location and pole-changing contacts operated by the neutral relay at that location; so arranged that a train occupying any section deenergizes the track relay thereof, said track relay releases the approach relay at the entrance end of the first section in advance, said approach relay releases the neutral relay at the entrance end of the second section in advance, and said neutral relay releases the polar relay at the entrance end of the third section in advance, said signal relays being efiective upon movement of a train through said stretch in the opposite direction to deenergize the polar relays for two sections in advance of the one occupied by the train moving in. said opposite direction, and means operated by each polar relay for operating the indicating means of its associated section to indicate the approach of a train, said first series of line circuits being thereby rendered effective to control the indicating means for either direction of trainlrnovement as Well as to control the signals for one direction of train movement.

References Cited in the file of this patent UNITED STATES PATENTS 2,083,274 Pelikan June 8, 1937 2,410,504 Judge Nov. 5, 1946 2,528,052 Grosjean Oct. 31, 1950 2,617,922 Thompson Nov. 11, 1952 2,618,740 Grosjean Nov. 18, 1952 2,630,524 Grosjean Mar. 3, 1953 

